This invention relates generally to an injecting unit for a molding machine and more particularly to a co-injecting unit for forming a molded article having an inner core and an outer skin.
A co-injection manifold is typically provided for a molding machine in which a core material and a skin material are concurrently injected into a mold cavity. The core material is typically a different material than the outer skin material. In some instances it may be desirable to use better quality plastic material as the observable outer surface or skin material and a cheaper lesser grade material as the non-visible core material.
Conventional co-injection manifolds include at least two inlets that feed a common outlet leading to the mold cavity. A valve and nozzle control the flow of each material through the outlet and into the mold. The valve provides the desired material flow into the mold and selectively shuts off flow of the core material such that the entire surface of a molded article is comprised of the desired outer skin material.
Co-injection manifolds typically utilize a similar grade of plastic materials that have similar melting temperatures. It is known to provide temperature control elements within a co-injection manifold to maintain the plastic material at a desired temperature. Plastic materials generally melt and are molded at similar temperatures and therefore the co-injection manifold is heated to a single common temperature.
Disadvantageously, separate or drastically different materials may require different temperatures. For example, recent developments utilize a wood or other cellulose material as the core for the molded article. The wood core material provides several benefits that provide advantages to the completed molded article. However, the wood material is not compatible with temperatures that are favorable to plastic material.
Accordingly, it is desirable to develop a co-injection manifold that provides separate temperature controls to provide for co-injection of a wood or other cellulose material and a plastic material through a common injection manifold.